It has previously been reported that the accumulation of albuminoid in lenses during the process of aging is associated with an increase in the cystine content of the lens proteins due to its presence in the albuminoid.* Evidence has, furthermore, been brought forward that in rat lenses this accumulation of cystine is due at least partly to an oxidation of cysteine of soluble lens proteins,1 and it has been pointed out that this oxidative process, which goes on during the life span of the rat, seems to be the result of a delicately balanced equilibrium of oxidative and reductive processes in the lens. This could be necessary for the integration of the albuminoid into the lenticular structure and, therefore, the maintenance of the transparency of the lens. It has long been known2 that the formation of senile cataract in man is accompanied by an increase of the albuminoid